Patent Document 1 discloses a technique of varying a control gain of a lock-up clutch of a torque converter according to a fluid temperature when slip-controlling the lock-up clutch.
However, in a case where the slip-control is affected by friction characteristics of the clutch, even though the control gain is varied according to the fluid temperature, it is difficult to achieve a proper slip-control.
The present invention was made in view of the above problem. An object of the present invention is therefore to provide a control device for the continuously variable transmission which is capable of achieving a stable engagement of the lock-up clutch.